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i have a marshal valvestate amp model 8040 when it has been on for awhile it goes very quiet and then comes on for a second and then off for 30 or so , any ideas ??? could this be a valve problem ???
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More than likely the power supply electrolytics need replacement.Originally posted by daggstar View Post
How old is the amp?See the birth of a 2-watt tube guitar amp - the "Dyno Tweed"
http://www.naturdoctor.com/Chapters/Amps/DynoTweed.html -
When you're talking about 'going off' you've got to be more specific. Is the power light going off and on, or are you just losing sound?Originally posted by daggstar View Post
If you're merely losing volume, and your amp has an effects loop, a dirty return jack is most likely the problem.
When the thing is quiet (exhibiting the symptom) plug an extra guitar cord into the RETURN jack, Now remove it. Repeat several times quickly. Likely as not this will bring full volume back. If it does, it means cleaning or replacing the jack. This is very common failure in guitar amps with an FX loop... especially if you don't usually use the loop jacks.
Regards,
BillComment
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the amp is probably around 16 years old . and it is a massive drop in volume. will try your advice about the jack trick , i presume that the pre amp out , power amp in , could be the problem as i have never used it .Comment
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marshall 8040 valve state amp
Hi all,
I had the same fault with this amp loss of power after 30 minutes and channel b had no tone control at all!
it turned out to be that the 33uf 450v cap had split open and the gain pot plus bass/mid control were damage due to misuse. after replacement of the first ic 1 and the valve / resistors /10uf caps plus many dry joints the amp is working as it should be.Comment
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